That's certainly true. But one doesn't require the axiom "only physical objects exist" to do physics, and that principal is not universally accepted among physicists.

This paper -- although I'm an outsider to physics, and I'm way more comfortable evaluating mathematics and computer science research -- seems like it has an interesting and novel approach to a theoretical problem in physics. I don't understand why the author felt the need to couple this with the given title and stress this point so much. It almost felt like click-bait, until I understood generally what was being done.